How the Marine Railway Works
The docking platform, often called a cradle, which the vessel sits on is supported by an inclined track that goes from the shore out into deeper water. A hauling chain is attached to the front end of the cradle and is fed up the inclined plane to a hauling machine and then back down under the cradle into the water and through a block; it is then fed back up the plane attaching to the back end of the platform. Because the chain is connected to both ends of the cradle you can think of it as a continuous loop much like a typical clothes line. In the hauling house large electric motors run a serious of gears that in turn pull the chain, causing the cradle to move up or down the inclined track.
In order for a vessel to properly be supported on the cradle engineers require a detailed hull schematic in order to create a proper blocking plan. A blocking plan is a plan that outlines the use of keel blocks and bilge blocks that are used to keep the vessel upright when out of the water. All blocking plans are unique to individual vessels and some can be very complex creating some challenges for engineers.